I figured since I was bored and had plenty of time to fool around loading and shooting I would see if I could lower my powder charge enough to eliminate the ejector swipe. Admittedly it is more of just a light shiny spot. Nothing seems to have been raised by pressure just a light shiny spot. Well I went low enough that the case just about wouldn't eject. Instead of the usual 6 feet out at in between 3 and 4 oclock it just sort of fell out of the gun. This is the minimum load that will function this particular AR. You guessed it still a light shiny spot. It occurs to me that the ejector being spring loaded will be sliding for a short distance across the face of the case as the bolt head turns. This might just be all there is to it. The brass being brand new Starline. At any rate I went the other way using the SMP 763 surplus powder and got really good accuracy until I hit a spot where 3 shots just barely edged over .5. Chrony says 2543 fps average. 120 grain Matchburners. Same exact shiny spot. Wonder if I kept adding powder at .3 grains a three shot group if accuracy would deteriorate around the time pressure gets a bit warm? I just can't come up with a definitive way to tell if I am loading too hot. Brass life? So far I have thrown exactly 3 cases away, all Hornady because primers got too easy to seat. Those cases were on their tenth or so firing. Maybe rounding the edges of the ejector would get rid of the swipe mark?
You didnt mention your barrel length but velocity is the best indicator of pressure. You can see velocity increase by adding .2-.3 a grain. Once the trend stops or spikes should be a warning or unusually high velocity for that barrel length and bullet weight.
rickt300 Wrote:This is the minimum load that will function this particular AR. You guessed it still a light shiny spot. It occurs to me that the ejector being spring loaded will be sliding for a short distance across the face of the case as the bolt head turns. This might just be all there is to it. The brass being brand new Starline.
It could be your overgassed. A pic of the shiny spot would help.
12-06-2023, 06:43 PM (This post was last modified: 12-06-2023, 06:46 PM by rickt300.)
Koda Wrote:It could be your overgassed. A pic of the shiny spot would help.
Well it is so small it is hard to make out and all cases don't show it. The primer is the relatively soft Federal 205. I figure going up a bit more should be fine?
rickt300 Wrote:Hard to take really good pictures with my cellphone it seems. I'm not seeing anything scary here.
agree nothing scary here, but there is something...
first, Im not the most experienced at this so if someone more experienced wants to critique my assessment feel free. But heres my experience
I had a similar mark on the case head on my 223 gas gun handload. An experienced reloader told me I was slightly overgassed. The "swipe" mark was actually caused by the extractor pulling the rim of the case back due to overgassing when the gas is trying to push the BCG back while the case is still expanded in the chamber resisting extraction. I purchased the next heavier buffer and it went away... no changes to my handload recipe.
12-07-2023, 03:56 AM (This post was last modified: 12-07-2023, 04:17 AM by Koda.)
.... continued...
Upon closer inspection (cheap jewlers loupe), the mark wasn't actually a radial shaped swipe mark but a line matching the profile of the extractor in the bolt face. Its always opposite the round ejector mark.
This is what I see in your case headstamps: the circle is the round ejector mark, the red line is the crease from the extractor trying to pull back on the rim before the case springs back from combustion (sealing the chamber). The telltale sign is the crease is always opposite the round ejector mark where a "swipe" would be randomly located. I suspect your slightly overgassed.
I edited your photo to show you what I see:
[ATTACH=CONFIG]20129[/ATTACH]
Upon closer inspection (cheap jewlers loupe), the mark wasn't actually a radial shaped swipe mark but a line matching the profile of the extractor in the bolt face. Its always opposite the round ejector mark.
This is what I see in your case headstamps: the circle is the round ejector mark, the red line is the crease from the extractor trying to pull back on the rim before the case springs back from combustion (sealing the chamber). The telltale sign is the crease is always opposite the round ejector mark where a "swipe" would be randomly located. I suspect your slightly overgassed.
I edited your photo to show you what I see:
[ATTACH=CONFIG]20129[/ATTACH]
Excellent post! The red line is covering what looks more like a light scratch instead of a crease. I notice that the .5 grain lighter load has a cleaner case head.
rickt300 Wrote:Excellent post! The red line is covering what looks more like a light scratch instead of a crease. I notice that the .5 grain lighter load has a cleaner case head.
a scratch and a crease can be pretty similar causes. I just think its interesting the marks are consistent on several samples. Im not there so I cant really say, just sharing my experience. It would be interesting to learn what you come up with as the solution.
Koda Wrote:a scratch and a crease can be pretty similar causes. I just think its interesting the marks are consistent on several samples. Im not there so I cant really say, just sharing my experience. It would be interesting to learn what you come up with as the solution.
Thinking about cleaning the edges off the ejector pin and the extractor. And dropping back .5 grains.
rickt300 Wrote:Thinking about cleaning the edges off the ejector pin and the extractor. And dropping back .5 grains.
I wouldn't modify the gun without knowing the cause of the swipe marks. You've already downloaded the powder cahrge and the mark is still there, not likely an handload issue.
My suggestion is your rifle is slightly overgassed and the extractor is bending the rim trying to extract the case before pressure has dropped in the chamber. This can also cause ejector swipes, falsely indicating pressure. You can adjust the gas block or increase buffer weight. New buffers are as little as 10-15 bucks, not a huge investment if it doesn't work out.
I was getting raised burrs when i was too hot for a brownells barrel. Was getting random ejector swipes on many loads that were mild in the load range data. Have also got marks on variois factory loads.
Expected it was just par for the course. Brass sized as easily as any factory fired cartrdige and didnt appear to have stretched any more than any other.
BluteEhre Wrote:I was getting raised burrs when i was too hot for a brownells barrel. Was getting random ejector swipes on many loads that were mild in the load range data. Have also got marks on variois factory loads.
Expected it was just par for the course. Brass sized as easily as any factory fired cartrdige and didnt appear to have stretched any more than any other.
The brass seems happy and easily reloaded. As for being slightly over gassed I am ok with that. Can high pressures mimick what over gassing causes?
rickt300 Wrote:The brass seems happy and easily reloaded. As for being slightly over gassed I am ok with that. Can high pressures mimick what over gassing causes?
yes, thats been my whole point in suggesting to rule out potential overgassing issues before diagnosing over pressure issues. Overgassing can cause ejector swipes. A heavier buffer is like 15 bucks.
There's another thing that could be at the root of this. A completely stock, squared-off ejector head can cause those marks as the case is being dragged out/rotated after firing. There are some threads on this at various times on the forum here. Many guys have taken to rounding off or beveling that ejector head, so the friction/dragging doesn't affect that bottom case surface. I did a few myself and it helped. I think though, for my others, I haven't got around to it yet.
Now I don't know what the load data is for shooter's world match (smp? right) but you may want to try some low to medium loads with some known grendel powder, to see if the marks still appear. If it is due to the square ejector face, then you'll get same marks with that powder as well.
One other tip may help if you want to go there, is to cut off 1, 1.5 or at most 2 coils from the ejector spring. Again, I tried that once and it helped too. Just don't cut off too many, you can't put them back lol.
"Down the floor, out the door, Go Brandon Go!!!!!"
Koda Wrote:yes, thats been my whole point in suggesting to rule out potential overgassing issues before diagnosing over pressure issues. Overgassing can cause ejector swipes. A heavier buffer is like 15 bucks.
Well I am running a rifle buffer in an A2 stock of course with a rifle length spring. 20 inch barrel mid length gas.
Shot 50 or so loads worked up with different powders and got pretty much the exact same results. Found a few loads that deserve more testing. Ragged hole groups. Is it possible that brand new brass might show the marks a bit more often than brass fired a couple times. On older brass It looks like nothing new has happened. Brass a bit soft?
rickt300 Wrote:Shot 50 or so loads worked up with different powders and got pretty much the exact same results. Found a few loads that deserve more testing. Ragged hole groups. Is it possible that brand new brass might show the marks a bit more often than brass fired a couple times. On older brass It looks like nothing new has happened. Brass a bit soft?
Maybe if your velocity is inside published velocities for your bullet weight then maybe its just soft brass and or a natural part of gas gun cycling, which is pretty hard on cases. If your not getting any other signs of pressure maybe just chalk it up to the abuse of gas gun operation and call it good.
![[Image: IMG-20231206-120516-198-jpg-brass2.jpg]](https://i.postimg.cc/KvgbYhTN/IMG-20231206-120516-198-jpg-brass2.jpg)
![[Image: IMG-20231206-144454-730.jpg]](https://i.postimg.cc/KjqgDqyZ/IMG-20231206-144454-730.jpg)
